The Science of Picky Eaters, Smart Marine Mammals,...

(Program not available for streaming.) What makes a dish taste good to some people and terrible to others? Why do many people, particularly many kids, find broccoli and spinach unbearably bitter? Neil deGrasse Tyson, whose mother says he was always a good eater, sets out to investigate the science behind our sense of taste. It turns out that genetics largely determine our taste, and specific genes may provide new excuses for picky eaters.

More Ways to Watch

The Science of Picky Eaters

Can
you imagine sitting down for a meal and getting served something that you know
will taste so bitter, so vile, but it's really good for you and you have no
choice but to eat it?

Thank
you.

For
some people out there this is just what it's like to eat foods that most others
find delicious. Why do people have such different reactions to the same thing?
Well, as I found out, the answer may just lie in their genes.

Nasty.

Some
kids love to eat, they'll eat almost anything. But others just hate the foods
that are best for them.

BOY:
I
don't like that green stuff. I don't want it.

NEIL
DeGRASSE TYSON:
Some kids are picky
eaters.

NEIL
DeGRASSE TYSON:
According to my
mom, I was never one of them.

SUNCHITA
TYSON:
Ever since he was a little toddler,
he ate everything that was put in front of him.

NEIL
DeGRASSE TYSON:
And it's a good
thing I did.

SUNCHITA
TYSON:
There was no question about being
picky. I didn't even know what the word meant.

NEIL
DeGRASSE TYSON:
So why are some
people picky and others not?

DANIELLE
R. REED
(Monell Chemical Senses Center): Just like we all differ in our ability to see and to
hear, people differ in their ability to taste.

NEIL
DeGRASSE TYSON:
What makes a dish
taste good to some people and terrible to others? I was determined to find out,
and I couldn't think of a better way to do it than to invite biologists Bob
Margolskee and Stuart Firestein for a tasty meal.

I
love good food, although it's still a mystery to me how my sense of taste
works. So, to set me straight, the chef and my colleagues came up with a little
experiment. Much to my surprise, it involved a lot more than my tongue.

STUART
FIRESTEIN:
All right, open wide, here it
comes. I want you to describe now, just what you're sensing in your mouth.

NEIL
DeGRASSE TYSON:
I don't taste
anything.

STUART
FIRESTEIN:
That's because flavor really
consists of several different sensory modalities. It's not just the taste in
your mouth...

NEIL
DeGRASSE TYSON:
Right.

STUART
FIRESTEIN:
...but also the way the food
smells in your nose, the way it looks on the plate, the way it feels in your
mouth.

NEIL
DeGRASSE TYSON:
Okay.

STUART
FIRESTEIN:
I'm going to take your nose plug
off, and I want you to breathe out while I do that. Okay, breathe out.

NEIL
DeGRASSE TYSON:
Wow, completely
different. Oh, it's fruit.

I
get some sort of sweet spices, like, I get a little bit of cinnamon, maybe a
little bit of clove.

STUART
FIRESTEIN:
So now let's take a look at
what you've been eating.

NEIL
DeGRASSE TYSON:
JELL-O.

So
why couldn't I taste it without my nose? Why should my nose have anything to do
with it at all?

STUART
FIRESTEIN:
Well I think evolution has seen
fit to devote as much of our sensory apparatus as possible to what we eat. You
are, after all, what you eat.

NEIL
DeGRASSE TYSON:
And so were our
caveman ancestors. They had to use all their senses to find the nutrients they
needed to survive in a hostile environment. And just like us, they probably
loved sweets. And there's an evolutionary reason for that: the sugar in sweet
foods provides a lot of energy.

ROBERT
F. MARGOLSKEE
(Monell Chemical Senses
Center): Sweet is very important
and most people strongly prefer sweet. This is a direct measure of the
nutritive value of a food.

NEIL
DeGRASSE TYSON:
On the other hand
we have a very different relationship with that bitter taste in many
vegetables. Bitter is a warning.

BOB
MARGOLSKEE:
Bitter is a protective sense. It's
a signal for something potentially poisonous. A plant puts out a toxic compound
so people won't eat it.

NEIL
DeGRASSE TYSON:
So the bitter
flavor in a plant prevents people from eating it. Our bitter taste buds honor
and respect that fact in a plant?

Stuart
and Bob assured me the answer to this taste bud mystery was on the tip of my
tongue.

These
are taste buds, and those long slender leaf-like shapes are taste cells. These
cells enable us to detect five basic flavors: sweet, salty, bitter, sour and umami,
the Japanese word for the savory taste in meat and cheese.

On
the outside of each taste cell are finger-like projections, covered with
hundreds of tiny taste receptors. And when those receptors bind with the foods
we eat, it opens a chemical pathway into the cell that leads all the way up to
the brain; that's what we call taste.

So,
why do some people hate that bitter taste found in green plants like broccoli
and Brussels sprouts and others, like me, enjoy it? It's all because of those
little taste receptors on your tongue, they're actually proteins, made by your
genes.

You've
heard of genes: they're subunits of our D.N.A., that long chain of four
chemicals, best known by their initials, A, C, G and T.

Biologists
have discovered that, out of the thousands of genes in our D.N.A., there's one
that determines if we like the taste of some healthy greens or if we can't
stand them.

And
that single gene was discovered by geneticist Dennis Drayna. He found it by
testing how strongly people react to the taste of P.T.C., a compound a lot like
the chemical found naturally in vegetables
like cauliflower and broccoli. While some people hate the taste of P.T.C,
others can't taste it at all.

Dennis
found the reason why, and it's in our genes.

DENNIS
DRAYNA:
Lo and behold, what did we find? We ultimately were
able to pinpoint the actual gene that causes this.

Ah
ha!

NEIL
DeGRASSE TYSON:
A gene that
determines how we perceive that bitter flavor in broccoli that so many people
hate.

So
I have this perfectly prepared salmon on this sauce of broccoli. As I chowed
down on a plate of healthy greens, I wanted to know just how this gene works,
and why it turns some of us into broccoli eaters and others into picky eaters.

Geneticist
Danielle Reed and bio-psychologist Julie Menella are finding answers to this
question with the help of middle school students like these.

DANIELLE
REED:
The experiment we're going to do
today is actually quite fun.

One,
two, three.

NEIL
DeGRASSE TYSON:
Students rub their cheeks
with a sterile swab, giving researchers easy access to a sample of their D.N.A.

Those
four letters in D.N.A., they're packed into 23 pairs of chromosomes. On one of
those pairs is the gene they're looking for.

DANIELLE
REED:
You get one chromosome from your mom
and one chromosome from you dad. So this chromosome might have a gene that's a
non-taster gene, and this chromosome from your dad might also be a non-taster
gene.

NEIL
DeGRASSE TYSON:
Non-tasters don't
taste the bitterness in many vegetables because they have the letters G-T-A in
that order in a certain spot on the gene. When you get G-T-A from your mom and
dad, those taste receptors on your tongue can't bind with the bitterness in
broccoli. But instead, if you get the letters C-C-G from both your mom and dad,
you can taste the bitterness in broccoli, and you're a "taster."

DANIELLE
REED:
And that makes you very sensitive to
bitter.

YOUNG
VOICE:
Oh, yuck!

NEIL
DeGRASSE TYSON:
Now, I bet you're
wondering what would happen if you got one of each.

DANIELLE
REED:
You might think of that as being a "medium
bitter-taster."

NEIL
DeGRASSE TYSON:
Over time, it may
be possible for medium bitter-tasters to actually learn to like the bitterness
in broccoli.

Back
in the lab, Danielle analyzes the kids' swabs. She thinks she can predict who
hates the bitterness of broccoli, based solely on their D.N.A.

She
then returns to the classroom to share the results with students and their
parents.

But
first, they give each kid some P.T.C. to drink.

As
she expects, some taste absolutely nothing, while others wished they'd stayed
home, especially Reed and Jarrod. When they see their D.N.A. results, it comes
as no surprise; they've both got the form of this gene which makes them very
sensitive to bitter. And guess what? Neither of them likes broccoli.

GAIL
MOMJIAN
(Reed's Mother)
:
She did come right over to me afterwards and said, "See,
I told you I don't like vegetables."

Maybe
I'll give her some slack.

ISA
WELSCH
(Jared's Mother): Yeah, I'll have a little more empathy, I guess, at
this point.

NEIL
DeGRASSE TYSON:
So what you're
telling me is that the picky-eating children are not accountable for being
picky eaters.

BOB
MARGOLSKEE:
It's in their genes.

NEIL
DeGRASSE TYSON:
It is biologically
predetermined. They are innocent in this accusatory world.

So
what's a parent to do with their picky eater?

Let them eat cake?

BOB
MARGOLSKEE:
My favorite part.

NEIL
DeGRASSE TYSON:
In the end, are we
really held hostage by our genes?

Oh,
man that's good.

Not
entirely.

Remember
at the beginning of my meal, when I found out just how much our senses work
together to create our perception of flavor? It turns out, over time, that our
sense of smell changes, and that affects our sense of taste, no matter what
kind of genes we have.

In
a recent study, my dining companion, Stuart Firestein found that of the
thousand genes in the mouse genome used for smell, not all of them are active
throughout life. Maybe the same is true for us.

STUART
FIRESTEIN:
And so, we think, over a
lifetime, our sense of smell changes. So that something which smelled really
bad, like, for example, Brussels sprouts or spinach, when we were a kid and
therefore gave us a bad feeling for the taste, now smells much better.

BOB
MARGOLSKEE:
So young children will avoid
bitter much more than the adult, and they are more sensitive and more
preferring of sweet. They have a sweet tooth. They like lots of fat, lots of
sugar.

NEIL
DeGRASSE TYSON:
What you're saying
is you have a biogenetic argument for why the children's menu at every single
restaurant in America doesn't have vegetables—no green
vegetables—and there's always something fried and an ice cream dessert at
the end.

STUART
FIRESTEIN:
Boy, that sounds good.

NEIL
DeGRASSE TYSON:
So next time you
get frustrated with your picky eater, take a moment to relax and remember,
their genes may be influencing their food choices just as much as you are.

On
Screen Text: Take 14 hydrogen atoms, 10 carbons, one oxygen
and put them together, and it smells like mint. Assemble that very same
molecule in a mirror image, and the same molecule, in this configuration,
smells like caraway. Why?

For
the most part, both molecules bind to the same receptors, but there are another
three receptors that bind only with the caraway version. And that's nothing to
sniff at. Sorry.

This material is based upon work
supported by the National Science Foundation under Grant No. 0638931. Any
opinions, findings, and conclusions or recommendations expressed in this
material are those of the author(s) and do not necessarily reflect the views of
the National Science Foundation.